CVE-2026-86049
highJupyter Server is the backend for Jupyter web applications.
Jupyter Server is the backend for Jupyter web applications. Prior to version 2.21.0, the 5xx request logging path in jupyter_server/log.py copies the Referer header into a JSON header block without applying the token scrubbing used for the request URI. A request that returns HTTP 500 while the Referer contains a token-bearing URL can therefore write that token to server logs in plaintext. An attacker who can read those logs can recover the token and use the affected user's Jupyter Server permissions. This issue is fixed in version 2.21.0.
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H Affected products
Not reported by the source (unknown — not "none").
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://github.com/jupyter-server/jupyter_server/commit/52513529af7096e622c00911b17627b266... security-advisories@github.com
- https://github.com/jupyter-server/jupyter_server/pull/1681 security-advisories@github.com
- https://github.com/jupyter-server/jupyter_server/releases/tag/v2.21.0 security-advisories@github.com
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-c3mw-737p-c7g2 security-advisories@github.com